1. Field of the Invention
The present invention relates to a superconducting circuit, more particularly to novel patterned superconducting wiring lines each made of a thin film of oxide superconductor deposited on a substrate and a process for fabricating the same.
2. Description of the Related Arts
The conventional superconductors exhibit the superconductive phenomenon only at extremely low temperature so that it has not been expected to be used in actual applications. In 1986, however, new oxide type superconductors of La, Ba!.sub.2 CuO.sub.4 and La, Sr!.sub.2 CuO.sub.4 were discovered and after then, discovery of the other superconducting compound oxides such as Y--Ba--Cu--O system or Bi--Ca--Sr--Cu--O system was continued. In these newly discovered oxide superconductors, the superconductive phenomenon can be realized with relatively cheaper liquid nitrogen and hence the possibility of an actual utilization of the high Tc superconductors have burst onto the scene.
Although these oxide superconductors were obtained initially in a bulk form of sintered block by powder sintering technique, now it becomes possible to prepare their thin films of high quality by physical vapour deposition or chemical vapour deposition techniques. The thin films of oxide superconductor are expected to be used in a variety of applications such as sensors, SQUID, superconducting devices including superconducting transistors and Josephson devices. In this specification, the term "oxide superconductor" means any high-Tc compound oxide which show the critical temperature of above 30 K.
In superconducting circuits having superconducting wiring lines, it is desirable to integrate patterned superconducting wiring lines in the same thin film of oxide superconductor as is used to fabricate the superconducting elements or devices. However, how to fabricate the patterned superconducting wiring lines in an integrated circuit have not been established.
It is known that the critical current density of oxide superconductor depend on the orientation of crystals of which a thin film of oxide superconductor is made and that the crystal possess anisotropy. This anisotropy limits the structure of a superconducting circuit including superconducting wiring lines made of a thin film of oxide superconductor.
An object of the present invention is to solve the problem and provides a novel structure of patterned superconducting wiring lines each made of a thin film of oxide superconductor deposited on a substrate and a process for fabricating the same, in order to increase the freedom of circuit designing and to make the best use of high Tc oxide superconductor.